Iran, which is also called Persia, is officially known as the Islamic Republic of Iran and is located in western Asia. Adjoining Iran to the north are Turkmenistan, Azerbaijan and Armenia, with Kazakhstan and Russia to the north across the Caspian Sea. Iran's east is bordered by Pakistan and Afghanistan, and its south is bordered by the Gulf of Oman and the Persian Gulf. It is bordered on the west by Iraq and on the northwest by Turkey. Due to its huge area, Iran is considered to be the 18th largest country of the world. It has a total population of around 78.5 million in 2014 (increased from 75 million in 2013), containing many different cultures and religions, and Iran offers freedom to practice and carry these out in their own ways. Moreover, Iran has the fourth largest petroleum reserves and largest natural gas reserves. As a mountainous country, it also holds great geographical importance.